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Bat bite packs clot-busting potential for strokes

Substance in animal's saliva may bring new treatment

Substance in animal's saliva may bring new treatment

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A stroke, sometimes called a "brain attack," occurs when a portion of the brain is deprived of oxygen due to a clogged artery or burst blood vessel. Without oxygen, the brain tissue and nerve cells can suffer permanent damage.

Source: National Heart Association

DALLAS, Texas (CNN) -- Stroke victims may get some help in the future from a bite from a vampire bat, new research suggests.

A substance taken from bats' saliva contains a powerful clot buster and may be used up to three times longer than the current stroke treatment and without additional risk for brain damage side effects, according to a study on mice in Thursday's issue of Stroke, published by the American Heart Association.

"When the vampire bat bites its victim, it secretes this powerful clot-dissolving substance so that the victim's blood will keep flowing, allowing the bat to feed," said Robert Medcalf, senior author of the study and researcher at Box Hill Hospital in Victoria, Australia, in a statement.

This bat enzyme is genetically related to current stroke medicines that break up clots, but it's more potent. Strokes are the third leading cause of deaths in the United States, according the Centers for Disease Control and Prevention. Ischemic strokes, which the study looked at, are caused when a blood clot or a series of clots block blood supply to the brain.

The bat saliva-derived clot buster is called desmoteplase, or DSPA. It targets and destroys the structural scaffold of blood clots, Medcalf said.

Currently, the only government approved clot buster for acute strokes is tissue plasminogen activator (t-PA), but it must be given to victims within three hours of the stroke to be effective. Any longer, and the risk of bleeding into the brain increases. It also has been shown to promote brain cell death in some animal studies.

Time on DSPA's side

In the current study, researchers injected the brains of mice with either DSPA or t-PA, and then tracked the survival of brain cells. They discovered that DSPA zeroed in on the blood clots but had no effect on brain receptors that can promote brain damage, Medcalf said.

In contrast, the traditional treatment of t-PA greatly enhanced the degree of brain cell death after time, and therefore may be harmful if administered too long after a victim's stroke.

Because the bat saliva clot-buster has no detrimental effect on brain cells, the time window of when it could be administered has greater potential for stroke treatment, the study says. The National Stroke Association says the average stroke patient waits more than 12 hours before going to the emergency room.

DSPA is being tested up to nine hours after stroke onset in human patients in Europe, Asia and Australia, with a possible U.S. study this year.

Dr. Larry Goldstein, chairman of the American Stroke Association Advisory Committee, believes the bat saliva-derived clot-buster has great potential over the one in current use, but he urged caution.

"It needs to be understood that this study is limited to mice without stroke and focused only on toxicity," he said. "Whether this approach will prove either safe of efficacious in improving stroke outcomes requires further testing."

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